Dyeing of cellulose esters with reduced vat dyes in alcoholic solution



i atented Aug. i950 .1

1DYEING OF CELLULOSE ESTERS WITH RE-i DUCED VAT DYES IN ALCOHOLIC SOLU-TION Edwin E. Laughlin, West Newton, Mass., and

1 Raymond W. Foulk, Bridgeport, N. J assignors to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application J anuary7, 1948,

Serial No. 1,066

This invention relates to the dyeingof cellulose esters, andmoreparticularly to the dyeing of fabrics composed of or containingcellulose esters, such as cellulose acetate, with vat dyes;

Vat dyes are used extensively in the dyeing of cellulose fibers such ascotton, regenerated cellulose's, etc., when it-is desired to impart tothose fibers colors having maximum fastness properties, especiallyfastness to light, weather and laundering. Because ,the vat dyes areusually applied to cellulose material from solutions having relativelyhigh alkalinity, they have not found general application in the dyeingof cellulose acetate or other esters'because the'highly alkaline vatcauses saponification of the cellulose ester with the result that thedesirable characteristics and advantages which the. cellulose acetatefibers possess over the viscose rayons is lost.

Cellulose acetate 1 and, other esters .are customarily dyed with acetatecolors, which, although they exhibit moderate to vfairlygood lightfastness, do not exhibit the fastness to Washing, especially repeatedwashing or laundering, that is desired, and some of the dyes of thisclass are sensitive to gas fume fading and undergo drastic.

changes in colorwhen the dyed material is exposed to fumes of burningnatural gas, oxides of nitrogen and other gases norm-ally present in theatmosphere, particularly in highly industrialized communities.

The fact that it has heretofore been impossible to dye celluloseacetatereadily in a range of colors which may be characterized as,fastin the same sense that fast colors are easily obtainable on othertextile fibers, such as cotton, regenerated celluloses, silk and wool,has materiallyretarded 2 Claims. (01. 8-36) the more-extensiveuse ofjcellulose, acetate as-a textile material. A continuingeffort is beingmade to provide a commercially feasible-process for dyeing celluloseacetate withdyeswhich have.

better fastness properties than thosethat are now available for generaluse on thatfiber, and-with a class of colors tha 3mi. et ii ra e, o

shades. H I v Previous attempts have beenmade to, dye cellulose acetatewith reduced vat'd'y'es'lfrom the usual vat'e'm ploye'd in the dyeing ofcotton'andregenerated celluloses, but it has been found that, if

the time of dyeing is"co'mparatively short, little or no color isimparted to the fiber, while-,fi'f a longer time of contact isemployed,'-the alkaline dye liquor causesf'saponification of thecellulose ester, resultingin the formation of somecenmese for which thedye'liquorhasgreaterisubstantivity' t an r the ell lo e ace a th rebycausing very uneven and undesirable dyeings. Another proposal has beento replace the strongv alkalies normally used in vat dyeings by Weakalkalies, However, such a process limits'the number of vat dyesapplicable and actually does not completely prevent saponification.

It is an object of this invention to provide'a process for dyeingcellulose acetate and related esters with vat dyes. A further object ofthe invention is to provide a commercially feasible process for thedyeing of cellulose acetate with vat dyes Without damage to the acetateand With-' out causing any material amount of saponification of the sameduring the dyeing process. Another object of the invention is toprovidea process for dyeing. celluloseacetate with all types of vat dyes. Astillfurther object of the invention is to permit vat dyeings ofcellulose acetate by a continuous process without saponification so thatall the excellent esthetic and physical properties of this valuable,fiber are retained. Further objects will appear'hereinafter.

We havefound that the above objects maybe very effectively accomplishedby maintaining a relatively high concentration of alcohol in thealkaline hydrosulfite vat ofthe vat dye together with a wetting agent, adispersing agent, and an additional type of adjuvant which We call avatstabilizing agent consisting of diethylene glycol, thiodiethyleneglycol, or glycerine. The cellulose ester absorbs in this manner asufficient amount of the dye liquor to impart the desired color thereto,and if the alkalinity of the solution in the fiber is quickly lowered toa pointwhere saponification of the fiber does not occur, verysatisfactory dyeings with the vat dye can b attained. By this method, wehave found-that the cellulose ester fiber itself is not harmed ordegraded and the dyed material possesses the excellent fastnessproperties usually associated with this type of dye when applied tocotton or regenerated cellulose.

The alcohol which acts as a swelling agent on the cellulose ester fiberpermits the leuco'vat dye to quickly penetrate into the fiber itself.For the purpose of our invention We have found that'alcohols having upto and including four carbon atoms, such as tertiary-butyl, propyl,isopropyl ncentration used,

alcohol should be fully miscible with Water at the V t it is necessaryto employ in the padding solution agents which will facilitate uniformwetting and swelling of the cellulose esters. In addition the leuco vatcolor must either be com pletely in solution or in a state of highlydispersed colloidal solution for successful operation. The use ofdispersing agents in aqueous systems has ng been used. We find thattheir use is helpful in our process, but the dispersing agents for usein the aqueous-alcohol media areby them-- selves not satisfactory whenthe final alcohol content in the solution is 30% to 60% which is withinthe scope of our invention. At such concentrations of alcohol the leucovat color quickly agglomerates and is precipitated. We have found thepad-bath. For the purpose of our invention this time may range generallyfrom four to ten seconds.

After padding through the aqueous alcohol solution, the fabric issqueezed sufficiently to prevent run-back of color on the fabric as itis carried over and under the guide rolls. We have found that withcellulose acetate the liquor retention by the fabric, or pick-up as itis called that certain agents which we call vat-stabilizing agents canbe used to enable the vat leuco tore main either dissolved or highlydispersed in the presence of such a great quantity of the alcohol.

The vat-stabilizing agents which we have found effective are:polyhydroxy alkyl compounds such as diethylene glycol, tliiodiethyl-eneglycol, or glycerine.

Any of the wetting agents usually employed in the dyeing or treating oftextile fibers be used in this process, such as the sodium salt. of the.sulfates of straight chain aliphatic alcohols containing eight or morecarbon atoms, the sodium salts of the allayl naphthalene sulfonic acidssuch as isopropylatecl naphthalene sulionic' acid, the sodium salts ofthe sulfonates of higher molecular weight aliphatic hydrocarbons, thesodium salts of sulfonated tetralin, etc.

The dispersing agents may be any of those suitablefor dispersing finelydivided solids in allal-ine solutions, such as sodiumligno:-sullfonates, the naphthalene beta-sulionic acid formaldehydecondensation products such as produced by the process of United StatesPatent 1,336,759, the triamine bases such as the trialkyl trimeth-ylenetri amines, etc;

The Wetting agent is. preferably employed in the dye bath in an amountranging from 0.1 to 4 ounces: r gallon. The dispersing agent and theglycerine or glycois may each be used in an amount ranging from 0 .25 to4 ounces per gallonof dye solution.

In practice, the material to be dyed maybe padded inthe alkalinehydrosulfite vat of" the vat. dye containing the alcohol, the swellingagent,.the dispersing agent, and the vat-stabilizing agent. The fabricis then passed immediately into a bathof lower alkalinity such as water,or, preferably,

a soda ash developmentbath of the type'described in United States Patent2,318,133. The cellulose ester is then rinsed, the dye oxidized, and thematerial dried.

For satisfactory operation as acontinuous process it is necessary thatthe temperature be sufiiciently high to insure prompt swelling oi thecellulose ester, but not so high that saponification of the fiber occursin any substantial amount, or that much of the alcohol isv lost byvaporization. We have found that in the padding operation temperaturesin the range of 110 F. to- 150 F. are operable, but the preferred rangeis 115 to 140 F. Below 110 F'. swelling of the fiber is slow, whileabove 150 F. saponifi'cation takes place. The time in the pad-bath mustvbe sufiicient to allow good swelling, but not so great thatsaponification of the fabric commences. The im-- mersion time depends onthe alcohol used, the

alcohol concentration and the temperature of in the trade, should be inthe range of 40% to based on the weight of the cloth, but the preferredrange is 50% to 70%.

The following examples are given to illustrate the invention. In theseexamples the ingredients added are based on ounces by weight per gallonof dye solution.

Example 1 A-two ounce per gallon pad liquor of Ponsol Golden Orange RRT(Color Index 1098) was prepared as follows:

2.0 oz. Ponsol Golden Orange RRT paste (1 color solids) 2.0 oz.potassium hydroxide 2.5 oz. sodium hyd-rosulfite 20oz. sodiumhydrocarbon sulfonate wetting agent (product of Example III of U. S. P.2,360,027.)

1.0 oz. naphthalene sulfonic' acid-formaldehyde condensation product 215oz. diethylene glycol Reduction was carried out. for 1 5 minutes at 140F. in 3.5 pints of water. The volume was made up to 0.5 gallon: withWater and then 0.5 gallon of ethyl alcohol. and 015 oz. of. triethyltriniethylenetria-mine were added- Cellulose acetate satin was paddedwith this liquor at 1 20 F1 for six seconds and at 55% pick-up, and wasthen immediately led intoan aqueous soda ash development bath for 60'secondsv at F. which contained:

- 1.00 oz./gal. soda ash 0.08 oz./ga1. potassium hydroxide 0.25 oz/gal.sodiumhydrosulfite 4.00 oz./ gal. common salt The fabric was thenoxidized by passing through a bathcontaining:

0.13 oz./gal. sodium dischromate 0.40 oz./ gal. acetic acid 28%Following this, the tabric was rinsed, soaped,

rinsed, and dried.

' The resultant fabric was uniformly dyed a pleasing reddish-orange ofexcellent fastness to light, crocking, perspiration and repeatedlaundering. Furthermore, the resultant fabric had not been damaged norsaponified. The class of dyes known as'direct dyes will dye viscoserayon readily and leave cellulose acetate unstained. The most sensitiveindication of saponification of cellulose acetate consists in subjectingthe material to the action of a direct dye bath. If even a trace ofsurface sap'onification has occurred, too small to be determined b thecustomary acetone solubility or hydrolysis tests, the material willnevertheless be stained by' the direct dye. In the above example, thematerial was'cross-dyed with Pontamine Sky Blue 63X, Color Index 518,and left completely unstained, indicating that there had been no traceofsaponification.

.fGolden Orange RRT2(Co1or Index=1098l pared'asfollowsa 0.5" oz. PonsolGolden "ma-aw pastln'a color sol1ds) I i 1.5 oz. potassium hydroxide I2.0 "02. "sodium hydrocarbon "Susann wetting agent (product of Example111 of U." SJ P. 2,366,027)

1.0 oz. naphthalene sulfonic acid-formaldehyde condensation product 2.5oz. diethylene glycol Reduction was carried out for minutes at 140 F. in3.5 pints of water. The volume was made up to 0.5 gallon of water, andthen 0.5 gallon of ethyl alcohol and 0.5 oz. of triethyl trimethylenetriamine were added.

The dyeing of the cellulose acetate satin was carried out as in Example1 to give equally satisfactory results.

Example 3 A four ounce per gallon pad liquor of Ponsol Golder Orange RRT(Color Index 1098) was prepared as follows:

4.0 oz. Ponsol Golden Orange RRT paste (11% color solids) 2.0 oz.potassium hydroxide 2.5 oz. sodium hydrosulfite 2.0 oz. sodiumhydrocarbon sulfate wetting agent (product of Example III of U. S. P.2,366,027)

1.0 oz. naphthalene sulfonic acid-formaldehyde condensation product 2.5oz. diethylene glycol Alkaline reduction was carried out for 15 minutesat 140 F. in 3.5 pints of water. The volume was made up to 0.5 gallon ofwater and 0.5 gallon of ethyl alcohol and 0.5 oz. of triethyltrimethylene tri-amine were added.

The cellulose acetate satin was then dyed and finished in the mannerdescribed in Example 1 above to give a dyeing which was equallysatisfactory.

Thiodiethylene glycol and glycerine maybe substituted in the aboveExamples 1, 2, and 3 for diethylene glycol and at the same concentrationto give equivalent effectiveness as vat stabilizing agents.

Example 4 The following vat colors were applied to cellulose acetatesatin by the process similar to that described in Examples 1, 2, and 3with equivalent satisfying results:

Sulfanthrene Yellow R supra -C. I. #1170 Sulfanthrene Orange R paste C.I. #1217 Vat dye of Example 3 of U. S. P. 1,234,171 Sulfanthrene Red 33paste C. I. #1212 Sulfanthrene Blue 2BD paste C. I. #1184 SulfanthreneBlue GR paste C. I. 969 Sulfanthrene Navy Blue MR paste C. I. #1183 Vatdye of Example 1 of U. S. P. 1,090,621 Ponsol YellowG double paste C. I.#1118 Ponsol Yellow AR double paste C. I. #1132 Ponsol Golden Orange Gpaste C. I. #1096 Ponsol Brown AG double paste C. I. #1152 Ponsol BrownAR double paste C. I. #1151 Ponsol Brown BB paste C. I. #1120 Vat dye ofExample 3 of U. S. P. 1,329,435

Ponsol Red BN double paste C. I. #1162 Ponsol Violet AR double paste C.I. #1135 P011 01 Brilliant Violet. 3B paste........... I. #1105 PonsolViolet 2RD paste C. I. #1104 Ponsol Red Violet RRNX paste C I. #1161Ponsol Blue BF double paste" C. 1.}?1113 Ponsol Blue GD double paste;C'."I.'#11'12 Ponsol Blue BCS- double paste LG. I. #1114 PonsolBrilliantBlue R paste C. I. til-106 Bonsol Blue 3G paste (;3;. I 1109 Vat dyeof-Example 1 of U. S. 1,761,624 -Ponsol-Dark Blue BR paste C. I.,# 1099n el de re n dQ 1 s ee---- 11354 .9 Vat dye of Example 2 of U. S. P.1,596,528 Ponsol Olive AR double paste C. I. #1150 Vat dye of U. S. P.995,396

Ponsol Black BA double paste C. I. #1102 The advantages of our inventionare obvious. We are enabled to dye cellulose ester fabrics with the fullrange of vat colors without the attendant disadvantages ofsaponification of the fiber. The result leads to a cellulose esterfabric dyed with the fastest line of dyestuff known today. The vatcolors also may'be applied in fairly heavy shades, and the deficienciesof poor fastness to light, rubbing, perspiration, washing, especiallyrepeated washing and laundering and gas fume fading are overcome by ourprocess. An especial advantage is the fact that the cellulose esterfabric after vat dyeing by our process shows no adverse effects ordeterioration but fully retains all of the esthetic properties ofpleasing handle and outstanding draping qualities inherent in this typeof fabric. A further advantage of our invention is that due to therapidity with which the process may be performed it is readilyapplicable to continuous process.

We claim:

1. A process of dyeing cellulose esters with vat dyes, which comprisespadding thecellulose ester material for a period no more than 10 secondswith an aqueous alkaline solution of a reduced vat dye containing in thesolution from 30% to 60% of alcohol, and, for each gallon of dye liquor,alkali in an amount equivalent to no more than 2.0 ounces of potassiumhydroxide, from 0.1 to 4 ounces of a wetting agent, 0.25 to 4 ounces ofa dispersing agent and from 0.25 to 4 ounces of a stabilizing agent ofthe group consisting of diethylene glycol, thiodiethylene glycol andglycerine, maintaining the pad bath temperature between 110 F. and F.and, immediately after padding, passing the material into an aqueoussolution having an alkalinity below that at which saponification of thecellulose ester takes place, and oxidizing the reduced vat dye on thematerial.

2. In a continuous process for dyeing cellulose acetate fibers, thesteps which comprise padding the fibers for a period no more than 10seconds with an aqueou alkaline solution of the reduced vat dyecontaining in the solution from 30% to 60% of alcohol, and, for eachgallon of dye liquor, alkali in an amount equivalent to no more than 2.0ounces of potassium hydroxide, from 0.1 to 4 ounces of a wetting agent,0.25 to 4 ounces of a dispersing agent and from 0.25 to 4 ounces of astabilizing agent of the group consisting of diethylene glycol,thiodiethylene glycol and glycerine, maintaining the pad bathtemperature between 110 F. and 150 F. and, immediately after padding,passing the impregnated fibers into a solution having an alkalinitybelow that at which saponification of the cellulose acetate takes place,and thereafter oxidizing the reduced vat dye on the fiber.

' EDWIN R. LAUGHLIN. RAYMOND W. FOULK.

(References an following page) 7 8 REFERENCES CITED H FOREIGN-PATENTSThe following references are of recotdjlrr'the Number Country Date fiIe.of this patent: 47936182 Great Britain Feb; 14,1938 e 847,107 FranceJune 26, 1939 N b UNHEDNSTATES PA'IENTSD t 7 583,349 Great Britain YDec. 16, 1946 um er am'e a e 1,398,357 Briggs Nov. 29,1921 OTHERREFERENCES 1,968,856 Rivat Aug. '7, 1934 Amer. Dye. Rep. forMay 21.,1945, page P212;

2 ,067,926 Kern Jan. 19", 193-7 R yon Textile Monthly for March 1947,page 2,090,511 Crossley AugxlT, 193-7 10 100 (155).; I

1. A PROCESS OF DYEING CELLULOSE ESTERS WITH VAT DYES, WHICH COMPRISESPADDING THE CELLULOSE ESTER MATERIAL FOR A PERIOD NO MORE THAN 10SECONDS WITH AN AQUEOUS ALKALINE SOLUTION OF A REDUCED VAT DYECONTAINING IN THE SOLUTION FROM 30% TO 60% OF ALCOHOL, AND, FOR EACHGALLON OF DYE LIQUOR, ALKALI IN AN AMOUNT EQUIVALENT TO NO MORE THAN 2.0OUNCES OF POTASIUM HYDROXIDE, FROM 0.1 TO 4 OUNCES OF A WETTING AGENT,0.25 TO 4 OUNCES OF A DISPERSING AGENT AND FROM 0.25 TO 4 OUNCES OF ASTABILIZING AGENT OF THE GROUP CONSISTING OF DIETHYLENE GLYCOL,THIODIETHYLENE GLYCOL AND GLYCERINE, MAINTAINING THE PAD BATHTEMPERATURE BETWEEN 110*F. AND 150*F. AND IMMEIATELY AFTER PADDING,PASSING THE MATERIAL INTO AN AQUEOUS SOLUTION HAVING AN ALKALINITY BELOWTHAT AT WHICH SAPONIFICATION OF THE CELLULOSE ESTER TAKES PLACE, ANDOXIDIZING THE REDUCED VAT DYE ON THE MATERIAL.